Project Summary Despite increasing evidence for a significant neurobiological basis to aggression, biological interventions have been largely side-stepped, despite the fact that violence is a global public health problem. An important need is to develop socially acceptable ways of bettering brain functioning to reduce adolescent behavior problems, a critical developmental stage for adult violence perpetration and mental health problems. This is the primary health challenge that this proposal aims to tackle. Our pilot data documents that omega-3, a long-chain fatty acid which is critical for brain structure and function, reduces behavior problems in children and adolescents six months after the end of supplementation. If we can further document support and extension of our pilot findings with dual supplementation to both parent and adolescent, and if we can begin to identify the mechanisms of action underlying change, this can provide a new vista on biological interventions for adolescent externalizing problems that predispose to violence. Our overarching, long-term goals are to develop a non-invasive biological approach to prevention of youth aggression, and ultimately adult violence. The specific aims of this 2 x 2 randomized, double-blind, stratified, placebo-controlled trial of omega-3 supplementation to adolescents and caregivers are: (1) to investigate whether a nutritional intervention to adolescents and their parents can reduce externalizing behavior problems; (2) to examine the impact of a dual nutritional intervention to both parents and adolescents on adolescent externalizing behavior problems; (3) to identify mechanisms of action by which omega-3 supplementation impacts externalizing behavior in adolescents. It is expected that omega-3 supplementation will reduce adolescent behavior problems, and that dual supplementation to both the caregiver and adolescent will result in exponential improvements in adolescent behavior. A secondary prediction is that improvements in neurocognitive functioning will partially account for any behavioral improvements observed. Effects on scholastic ability are also explored. The paradigm-shift that could influence clinical practice is the use of a biological intervention that is not solely focused on the adolescent, but which is also applied to the primary caregiver. To our knowledge, such dual supplementation has never been examined. From an epidemiological standpoint, if this dual intervention approach could reduce even modestly the overall level of aggressive and antisocial behavior in the community at large, there is the promise of enhancing child health and development with a clinical paradigm novel in the biological study of behavior problems. The study's significance extends beyond adolescent behavior problems, which predispose not just to later adult violence, but also a wide array of adult psychiatric disorders. These adult outcomes result in an enormous societal burden in terms of economic costs, reduced occupational functioning, social functioning, and quality of life for both victims and perpetrators, a burden which could be significantly ameliorated if our pilot findings are supported.